This invention relates to a running tool for delivering a hanger into a well and, in particular, to a running tool which not only delivers the hanger into the well, but which also can be used to assist in applying the necessary tension to the hanger. The invention described in the current application finds particular benefit when used in conjunction with a system for rotating an element inside a pressure containing housing as set out in the applicant's co-pending European patent application no. EP07119220.7.
Accordingly, the running sleeve to which the present invention relates is particularly useful when used with a type of wellhead system known as “Tie back” which is used on wells with pre-drilled casing strings which are suspended at the seabed or mudline.
Whilst specifically applicable to this type of wellhead system, the invention may be used in other applications in which rotation of an element in a pressure containing housing is required.
In order to connect pre-drilled casing strings to a wellhead at the surface, which is typically located on a production platform, a means has to be provided in the surface wellhead to place the mudline to surface (tie back) casing strings in tension.
This requires that the casing suspension mechanism (hanger) within the wellhead provides a means of adjustment which conventionally comprises a threaded hanger landing ring. This ring is mounted on the casing hanger and is rotated, such that it is moved axially down the body of the casing hanger whilst the hanger is held at the required tension by tubular members that pass back to the surface. The landing ring is rotated by means of an engaging tool, which is in turn rotated by tubular members passing back to the surface, these tubular members being external to and concentric with the internal tubular member which are holding the casing hanger in tension. The landing ring is rotated down the body of the casing hanger until it abuts a landing shoulder such that the applied tension on the hanger cannot be released.
However, such an arrangement requires many different trips with various tools into the wellhead in order to apply the necessary tension, as the running tool itself cannot be utilised in an appropriate way such that the tension can be applied whilst the running tool is in place.
Accordingly, the present invention aims to provide a running tool which can be used for delivering a hanger into a well and which allows the necessary rotation and thereby tensioning to be applied to the hanger whilst the running tool is in place.